Polycrystalline diamond compact

ABSTRACT

Embodiments of the invention relate to polycrystalline diamond compacts (“PDCs”) and methods of fabricating such PDCs. In an embodiment, a PDC includes a substrate and a preformed polycrystalline diamond table including an interfacial surface bonded to the substrate and an opposing working surface. The preformed polycrystalline diamond table includes a proximal region extending from the interfacial surface to an intermediate location within the preformed polycrystalline diamond table that includes a metallic infiltrant infiltrated from the substrate, and a distal region extending from the working surface to the intermediate location that is substantially free of the metallic infiltrant. A boundary exists between the proximal and distal regions that has a nonplanar irregular profile characteristic of the metallic infiltrant having been infiltrated into the preformed polycrystalline diamond table.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.12/271,081 filed on 14 Nov. 2008, which is a continuation-in-part ofU.S. patent application Ser. No. 11/983,619 filed on 9 Nov. 2007 (nowU.S. Pat. No. 8,034,136 issued 11 Oct. 2011), which claims the benefitof U.S. Provisional Application No. 60/860,098 filed on 20 Nov. 2006 andU.S. Provisional Application No. 60/876,701 filed on 21 Dec. 2006, thedisclosures of each of the preceding applications are incorporatedherein, in their entirety, by this reference.

BACKGROUND

Wear-resistant, superabrasive compacts are utilized in a variety ofmechanical applications. For example, polycrystalline diamond compacts(“PDCs”) are used in drilling tools (e.g., cutting elements, gagetrimmers, etc.), machining equipment, bearing apparatuses, wire-drawingmachinery, and in other mechanical apparatuses.

PDCs have found particular utility as superabrasive cutting elements inrotary drill bits, such as roller cone drill bits and fixed cutter drillbits. A PDC cutting element typically includes a superabrasive diamondlayer (also known as a diamond table). The diamond table is formed andbonded to a substrate using a high-pressure/high-temperature (“HPHT”)process. The PDC cutting element may also be brazed directly into apreformed pocket, socket, or other receptacle formed in a bit body. Thesubstrate may often be brazed or otherwise joined to an attachmentmember, such as a cylindrical backing. A rotary drill bit typicallyincludes a number of PDC cutting elements affixed to the bit body. It isalso known that a stud carrying the PDC may be used as a PDC cuttingelement when mounted to a bit body of a rotary drill bit bypress-fitting, brazing, or otherwise securing the stud into a receptacleformed in the bit body.

Conventional PDCs are normally fabricated by placing a cemented-carbidesubstrate into a container or cartridge with a volume of diamondparticles positioned adjacent to the cemented-carbide substrate. Anumber of such cartridges may be loaded into a HPHT press. Thesubstrates and volume of diamond particles are then processed under HPHTconditions in the presence of a catalyst material that causes thediamond particles to bond to one another to form a matrix of bondeddiamond grains defining a polycrystalline diamond (“PCD”) table that isbonded to the substrate. The catalyst material is often a metal-solventcatalyst (e.g., cobalt, nickel, iron, or alloys thereof) that is usedfor promoting intergrowth of the diamond particles.

In one conventional approach, a constituent of the cemented-carbidesubstrate, such as cobalt from a cobalt-cemented tungsten carbidesubstrate, liquefies and sweeps from a region adjacent to the volume ofdiamond particles into interstitial regions between the diamondparticles during the HPHT process. The cobalt acts as a catalyst topromote intergrowth between the diamond particles, which results information of bonded diamond grains. Often, a solvent catalyst may bemixed with the diamond particles prior to subjecting the diamondparticles and substrate to the HPHT process.

The presence of the solvent catalyst in the PCD table is believed toreduce the thermal stability of the PCD table at elevated temperatures.For example, the difference in thermal expansion coefficient between thediamond grains and the solvent catalyst is believed to lead to chippingor cracking of the PCD table during drilling or cutting operations,which can degrade the mechanical properties of the PCD table or causefailure. Additionally, some of the diamond grains can undergo a chemicalbreakdown or back-conversion to graphite via interaction with thesolvent catalyst. At elevated high temperatures, portions of diamondgrains may transform to carbon monoxide, carbon dioxide, graphite, orcombinations thereof, thereby degrading the mechanical properties of thePCD table.

One conventional approach for improving the thermal stability of a PCDtable of a PDC is to at least partially remove the solvent catalyst fromthe PCD table by acid leaching. Another conventional approach forforming a PDC includes separately forming a sintered PCD table that issubsequently leached to remove solvent catalyst from interstitialregions between bonded diamond grains. The leached PCD table may bebonded to a substrate and infiltrated with a non-catalyst material, suchas silicon, in a separate HPHT process. The silicon may infiltrate theinterstitial regions of the leached PCD table from which the solventcatalyst has been leached and react with the diamond grains to formsilicon carbide.

Despite the availability of a number of different PDCs, manufacturersand users of PDCs continue to seek PDCs that exhibit improved toughness,wear resistance, thermal stability, and/or ease of processing.

SUMMARY

Embodiments of the invention relate to PDCs and methods of fabricatingsuch PDCs. In an embodiment, a PDC includes a substrate and apre-sintered PCD table bonded to the substrate. Such a PDC may bedescribed as a “two-step” compact. The pre-sintered PCD table includesbonded diamond grains defining interstitial regions. At least a portionof the interstitial regions include at least one material disposedtherein selected from the group of a silicon-cobalt alloy, siliconcarbide, cobalt carbide, and a mixed carbide of silicon and cobalt. Thepre-sintered PCD table lacks an intermediate contaminant region thereinthat includes at least one type of fabrication by-product generatedduring the fabrication of the pre-sintered PCD table and/or bonding thepre-sintered PCD table to the substrate.

In an embodiment, a method of fabricating a PDC includes positioning asilicon-cobalt containing layer between a substrate and an at leastpartially leached PCD table having interstitial regions therein to forman assembly. The method further includes subjecting the assembly to anHPHT process to infiltrate the interstitial regions with a liquidcomprising silicon and cobalt from the silicon-cobalt containing layer.

In an embodiment, a method of fabricating a PDC includes positioning anat least partially leached PCD table having interstitial regions thereinbetween a substrate and a silicon-cobalt containing layer to form anassembly. The method further includes subjecting the assembly to an HPHTprocess to infiltrate the interstitial regions with a liquid comprisingsilicon and cobalt from the silicon-cobalt containing layer.

In an embodiment, a PDC includes a substrate and a pre-sintered PCDtable. The pre-sintered PCD table includes an interfacial surface bondedto the substrate and an opposing working surface. The pre-sintered PCDtable includes a proximal region extending from the interfacial surfaceto an intermediate location within the pre-sintered PCD table thatincludes a metal-solvent catalyst infiltrant infiltrated from thesubstrate and a distal region extending from the working surface to theintermediate location that is substantially free of the metal-solventcatalyst infitrant. Portions of the metal-solvent catalyst infiltrantexposed through the distal region have a surface structurecharacteristic of not being chemically etched.

In an embodiment, a method of fabricating a PDC includes positioning anat least partially leached PCD table adjacent to a substrate to form anassembly. The method further includes subjecting the assembly to an HPHTprocess to infiltrate the at least partially leached PCD table with aninfiltrant from the substrate to no further than an intermediatelocation within the at least partially leached PCD table.

In an embodiment, a PDC includes a substrate and a pre-sintered PCDtable including an interfacial surface bonded to the substrate and anopposing working surface. The pre-sintered PCD table includes bondeddiamond grains defining interstitial regions. The pre-sintered PCD tableincludes a working region that extends inwardly from the workingsurface. At least a portion of the interstitial regions of the workingregion include silicon carbide and tungsten.

In an embodiment, a method of fabricating a PDC includes forming an atleast partially leached PCD table including a first surface and anopposing second surface. The at least partially leached PCD tableincludes bonded diamond grains defining interstitial regions. The atleast partially leached PCD table includes a first working regionextending from the first surface to an intermediate location thereinhaving tungsten, tungsten carbide, or combinations thereof disposed inat least some of the interstitial regions thereof and a second regionextending inwardly from the second surface that is substantially free oftungsten. The method also includes positioning the second region atleast proximate to a substrate to form an assembly. The method furtherincludes subjecting the assembly to an HPHT process to form the PDC.

In an embodiment, a method of fabricating a PDC includes disposing amass of diamond particles between a substrate and a metal-solventcatalyst layer to form an assembly. The metal-solvent catalyst layer issubstantially free of tungsten and/or tungsten carbide. The method alsoincludes infiltrating the mass of diamond particles partially withmetal-solvent catalyst from the metal-solvent catalyst layer andpartially with a metal-solvent catalyst constituent from the substrateunder high-pressure/high-temperature conditions that promote sinteringof the diamond particles to form a PCD table bonded to the substrate.The method further includes removing at least a portion of themetal-solvent catalyst from the PCD table.

Other embodiments relate to applications utilizing the disclosed PDCs invarious articles and apparatuses, such as rotary drill bits, miningtools and drill bits, bearing apparatuses, wire-drawing dies, machiningequipment, and other articles and apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, whereinidentical reference numerals refer to identical elements or features indifferent views or embodiments shown in the drawings.

FIGS. 1A-1C are cross-sectional views illustrating various stages in anembodiment of a method for fabricating a PDC and the PDC so-formed.

FIGS. 2A and 2B are cross-sectional views illustrating various stages inan embodiment of a method for fabricating a PDC by only partiallyinfiltrating an at least partially leached PCD table with metal-solventcatalyst and the PDC so-formed.

FIGS. 3A-3E are cross-sectional views illustrating various stages in anembodiment of a method for fabricating a PDC and the PDC so-formed.

FIGS. 4A-4C are cross-sectional views illustrating various stages in anembodiment of a method for fabricating a PDC in a single HPHT processand the PDC so-formed.

FIG. 5A is an isometric view of an embodiment of a rotary drill bit thatmay employ one or more of the disclosed PDC embodiments.

FIG. 5B is a top elevation view of the rotary drill bit shown in FIG.5A.

FIG. 6A is a perspective view of an embodiment of a mining rotary drillbit.

FIG. 6B is a side elevation view of the mining rotary drill bit shown inFIG. 6A.

FIG. 6C is a top elevation view of the mining rotary drill bit shown inFIG. 6A.

FIG. 7 is an isometric cut-away view of an embodiment of athrust-bearing apparatus that may utilize any of the disclosed PDCembodiments as bearing elements.

FIG. 8 is an isometric cut-away view of an embodiment of a radialbearing apparatus that may utilize any of the disclosed PDC embodimentsas bearing elements.

FIG. 9 is a schematic isometric cut-away view of an embodiment of asubterranean drilling system including the thrust-bearing apparatusshown in FIG. 7.

FIG. 10 is a side cross-sectional view of an embodiment of awire-drawing die that employs a PDC fabricated in accordance with theprinciples described herein.

DETAILED DESCRIPTION

Embodiments of the invention relate to PDCs and methods of fabricatingsuch PDCs. The PDC embodiments disclosed herein may be used in a varietyof applications, such as rotary drill bits, mining tools and drill bits,bearing apparatuses, wire-drawing dies, machining equipment, and otherarticles and apparatuses.

FIGS. 1A-1C are cross-sectional views illustrating various stages in anembodiment of a method for fabricating a PDC and the PDC so-formed.Referring to FIG. 1A, an assembly 100 may be formed by positioning asilicon-cobalt containing layer 102 between a substrate 104 and an atleast partially leached PCD table 106. The at least partially leachedPCD table 106 includes a first surface 108 and an opposing secondinterfacial surface 110 positioned adjacent to the silicon-cobaltcontaining layer 102. The at least partially leached PCD table 106 alsoincludes a plurality of interstitial regions that were previouslyoccupied by a metal-solvent catalyst and form a network of at leastpartially interconnected pores that extend between the first surface 108and second interfacial surface 110.

The silicon-cobalt containing layer 102 may comprise a mixture ofsilicon particles and cobalt particles. In one embodiment, thesilicon-cobalt containing layer 102 comprises silicon particles presentin an amount of about 50 to about 60 weight percent (“wt %”) and cobaltparticles present in an amount of about 40 to about 50 wt %. In a morespecific embodiment, the silicon-cobalt containing layer 102 comprisessilicon particles and cobalt particles present in an amount of aboutequal to or near a eutectic composition of the silicon-cobalt chemicalsystem. In some embodiments, the silicon particles and cobalt particlesmay be held together by an organic binder to form a green layer ofcobalt and silicon particles. In another embodiment, the silicon-cobaltcontaining layer 102 may comprise a thin sheet of a silicon-cobalt alloyor a green layer of silicon-cobalt alloy particles formed by mechanicalalloying having a low-melting eutectic or near eutectic composition.

The at least partially leached PCD table 106 may be fabricated bysubjecting a plurality of diamond particles (e.g., diamond particleshaving an average particle size between 0.5 μm to about 70 μm) to a HPHTsintering process in the presence of a metal-solvent catalyst, such ascobalt, nickel, iron, or alloys thereof to facilitate intergrowthbetween the diamond particles and form a PCD table comprised of bondeddiamond grains (i.e., diamond-to-diamond bonding) defining interstitialregions with the metal-solvent catalyst disposed within the interstitialregions. The diamond particles may exhibit a single mode or a bimodal orgreater diamond particle size distribution. The as-sintered PCD tablemay be leached by immersion in an acid, such as aqua-regia, a solutionof nitric acid, or subjected to another suitable process to remove atleast a portion of the metal-solvent catalyst from the interstitialregions of the polycrystalline diamond table and form the at leastpartially leached PCD table 106. For example, the as-sintered PCD tablemay be immersed in the acid for about 2 to about 7 days (e.g., about 3,5, or 7 days).

Suitable materials for the substrate 104 include, without limitation,cemented carbides including titanium carbide, niobium carbide, tantalumcarbide, vanadium carbide, tungsten carbide, and combinations of any ofthe preceding carbides cemented with iron, nickel, cobalt, or alloysthereof. For example, the substrate 104 may comprise a cemented-carbidematerial, such as a cobalt-cemented tungsten carbide material and/oranother suitable material.

As a result of the leaching process used to remove the metal-solventcatalyst, the at least partially leached PCD table 106 may includeleaching by-products. For example, the solution used to remove, forexample, cobalt from the interstitial regions may leave one or moretypes of residual salts, one or more types of oxides, combinations ofthe foregoing, or another leaching by-product within at least some ofthe interstitial regions of the at least partially leached PCD table106. For example, depending upon the chemistry of the leaching solution,the leaching by-products may comprise a salt of nitric acid, a salt ofhydrochloric acid, a salt of phosphoric acid, a salt of acetic acid, ametal oxide, or mixtures of the foregoing. For example, the salt may becobalt nitrate, cobalt chloride, or combinations thereof. For example,the metal oxide may comprise an oxide of tungsten, an oxide of cobalt,or an oxide of any metal-solvent catalyst, and/or an oxide of anothertype of metal present in the catalyst of the at least partially leachedPCD table 106 prior to leaching. It is currently believed that suchleaching by-products may block, obstruct, or otherwise inhibitinfiltration of the at least partially leached PCD table 106 with acatalyst, such as cobalt, when the at least partially leached PCD table106 is bonded to a substrate. Additionally, such leaching by-productsmay inhibit back filling with a non-catalyst material such as silicon.

The assembly 100 may be placed in a pressure transmitting medium, suchas a refractory metal can, graphite structure, pyrophyllite or otherpressure transmitting structure, or another suitable container orsupporting element. The pressure transmitting medium, including theassembly 100, may be subjected to a HPHT process using a HPHT press tocreate temperature and pressure conditions at which diamond is stable.The temperature of the HPHT process may be at least about 1000 Celsius(e.g., about 1300 Celsius to about 1600 Celsius) and the pressure of theHPHT process may be at least 4.0 GPa (e.g., about 5.0 GPa to about 9.0GPa) for a time sufficient to bond the at least partially leached PCDtable 106 to the substrate 104 and form an intermediate PDC 112 as shownin FIG. 1B having an infiltrated PCD table 114 bonded to the substrate104.

The temperature of the HPHT process is sufficient to cause thesilicon-cobalt containing layer 102 to melt and a liquid comprisingsilicon and cobalt infiltrates into the interstitial regions of the atleast partially leached PCD table 106. As the liquefied silicon-cobaltcontaining material infiltrates the at least partially leached PCD table106, leaching by-products present in the at least partially leached PCDtable 106 and/or other fabrication by-products (e.g., hydrogen or othergases from air) may be driven toward the first surface 108 into a thinwaste region 116. As used herein, the phrase “fabrication by-products”encompasses leaching by-products generated during leaching ofmetal-solvent catalyst from a PCD table to form an at least partiallyleached PCD table and gaseous impurities that become trapped inside aPCD table during HPHT bonding of an at least partially leached PCD tableto a substrate. An intermediate region 118 of the PCD table 116 issubstantially free of the fabrication by-products and includes at leastone of the following materials disposed in the interstitial regionsthereof: a silicon-cobalt alloy, silicon carbide, cobalt carbide, and amixed carbide of silicon and cobalt. For example, the silicon-cobaltalloy may include a silicon phase and cobalt silicide phase, such asCoSi₂. Silicon carbide, cobalt carbide, and a mixed carbide of siliconand cobalt may be formed by silicon, cobalt, and a silicon-cobalt alloy,respectively, by reacting with diamond grains of the at least partiallyleached PCD table 106 during the HPHT process. The temperature of theHPHT process is also sufficient to liquefy a metal-solvent catalyst(e.g., cobalt, nickel, iron, or alloys thereof) in the substrate 104 andinfiltrate the interstitial regions of the at least partially leachedPCD table 106. The metal-solvent catalyst infiltrated from the substrate104 occupies the interstitial regions in a region 120 adjacent to thesubstrate 104 to form a strong metallurgical bond between the PCD table114 and the substrate 104. In some embodiments, the volume of thesilicon-cobalt containing layer 102 may be selected so that region 120is relatively thin compared to the intermediate region 118, andinfiltrated material from the silicon-cobalt containing layer 102occupies at least a majority of the interstitial regions of the PCDtable 114.

Referring to FIG. 1C, the thin waste region 116 may be removed from thePCD table 114 using a suitable material removal process to form aworking region 122 including a working surface 124 that may come intocontact with a subterranean formation during drilling. For example,suitable material removal processes include grinding, lapping, andelectro-discharge machining. The working region 122 may still beconsidered thermally stable because the cobalt may be present in theform of a carbide, a mixed carbide, a silicide, or combinations thereofand cobalt in such forms does not substantially function todetrimentally affect the diamond during use. Furthermore, becausesubstantially all of the fabrication by-products present in the at leastpartially leached PCD table 106 may be driven into the thin waste region116 and subsequently removed, the PCD table 114 lacks an intermediatecontaminant region therein having fabrication by-products. Such anintermediate contaminant region may be of indeterminate shape/dimensionsand located below the working surface 124 and between the interfacialsurface 110 and the working surface 124. For example, such anintermediate contaminant region having a thickness significantly lessthan the thickness of the PCD table 114 and located about halfwaybetween the working surface 124 and the interfacial surface 110 of thePCD table 114. An intermediate contaminant region including fabricationby-products may be formed when silicon is infiltrated into the at leastpartially leached PCD table 106 from the first surface 108 andmetal-solvent catalyst is infiltrated into the at least partiallyleached PCD table 106 from the second surface 110 because thefabrication by-products may be driven to an intermediate contaminantregion between the first and second surfaces 108 and 110. Moreover, suchan intermediate contaminant region often may include stress crackstherein that may result in premature mechanical failure. Accordingly,the PCD table 114 may also lack stress cracks at an intermediate depththerein.

It is also noted that the transitional stresses between the intermediateregion 118 and region 120 may be lessened compared to if cobalt were notpresent in the silicon-cobalt containing layer 102. It is currentlybelieved that the transition stresses are moderated because of thepresence of cobalt in the interstitial regions of the intermediateregion 118, which moderates the transitional stresses from theintermediate region 118 to the region 120 so that stress cracks do notgenerally occur at the interface between the intermediate region 118 andregion 120.

In another embodiment, the at least partially leached PCD table 106 maybe positioned between the substrate 104 and silicon-cobalt containinglayer 102 to form an assembly. The assembly may be subjected to a HPHTprocess using the same or similar conditions used to HPHT process theassembly 100 to form a PDC. The PDC so-formed includes a PCD tablehaving the same or very similar construction as the PCD table shown inFIG. 1C. Optionally, the assembly may be vacuum sealed. Vacuum sealingthe assembly may prevent impurities from air becoming entrapped in theat least partially leached PCD table 106 during the HPHT process becauseinfiltration by material from the silicon-cobalt containing layer 102will not drive such fabrication by-products into an upper waste regionthat can be removed unlike the embodiment described with respect toFIGS. 1A-1C. The at least partially leached PCD table 106 may becleaned, prior to HPHT bonding to the substrate 104 to remove leachingby-products therefrom, using any of the cleaning techniques disclosed inU.S. patent application Ser. No. 12/120,949, the disclosure of which isincorporated herein, in its entirety, by this reference.

FIGS. 2A and 2B are cross-sectional views illustrating various stages inan embodiment of a method for fabricating a PDC by only partiallyinfiltrating an at least partially leached PCD table with metal-solventcatalyst and the PDC so-formed. Referring to FIG. 2A, an at leastpartially leached PCD table 106 is formed and provided as previouslydescribed with respect to FIGS. 1A-1C. An assembly 200 is formed bypositioning the at least partially leached PCD table 106 adjacent to asubstrate 104 that includes a metal-solvent catalyst therein, such as acobalt-cemented tungsten carbide substrate.

Referring to FIG. 2B, the assembly 200 may be subjected to a HPHTprocess to partially infiltrate the at least partially leached PCD table106 with a metal-solvent catalyst infiltrant from the substrate 104 tono further than an intermediate location within the at least partiallyleached PCD table 106 to form a partially infiltrated PCD table 202. Themetal-solvent catalyst infiltrant occupies the interstitial regionsbetween bonded diamond grains in a proximal region 204 adjacent to thesubstrate 104 to form a strong metallurgical bonded between thesubstrate 104 and the interfacial surface 110 of the partiallyinfiltrated PCD table 202. When the substrate 104 is a cemented tungstencarbide substrate, the metal-solvent catalyst infiltrant may sweep intungsten and/or tungsten carbide. The tungsten may be present in analloy with the metal-solvent catalyst infiltrant (e.g., acobalt-tungsten alloy), substantially pure tungsten, and/or as tungstencarbide. A distal region 206 remote from the substrate 104 issubstantially free of metal-solvent catalyst infiltrant. However, theremay still be residual amounts of metal-solvent catalyst used tofabricate the at least partially leached PCD table 106 that were notremoved during the leaching process used to deplete the at leastpartially leached PCD table 106 of such metal-solvent catalyst. Thedistal region 206 extends from the first surface 108 (i.e., a workingsurface) of the partially infiltrated PCD table 202 to an intermediatedepth d. The intermediate depth d may be at least about 50 μm, such asabout 50 μm to about 2000 μm.

Still referring to FIG. 2B, a boundary 210 between the proximal region204 and distal region 206 may be apparent from microstructural analysisand structurally distinguishable from a PDC formed by completelyinfiltrating the at least partially leached PCD table 106 and leachingmetal-solvent catalyst from the completely infiltrated PCD table to adepth d. For example, portions of the metal-solvent catalyst infiltrantof the proximal region 204 exposed through at least partially emptyinterstitial regions of the distal region 206 at the boundary 210 maynot exhibit a roughened surface characteristic of being formed by aleaching/etching process. Thus, the portions of the metal-solventcatalyst infiltrant exposed through the distal region have a surfacestructure characteristic of not being chemically etched. Only partiallyinfiltrating the at least partially leached PCD table 106 eliminates atime consuming and costly manufacturing step of leaching a fullyinfiltrated PCD table. It is noted that although the boundary 210 isillustrated as being substantially uniform, the boundary 210 may exhibita non-planar geometry such as an irregular boundary profile.

The distance that the metal-solvent catalyst infiltrant infiltrates intothe at least partially leached PCD table 106 may be controlled byselecting the pressure, temperature, and/or process time employed in theHPHT process. In one embodiment, the assembly may be subjected to atemperature of about 1150 Celsius to about 1300 Celsius (e.g., about1270 Celsius to about 1300 Celsius) and a corresponding pressure that iswithin the diamond stable region, such as about 5.0 GPa. Suchtemperature and pressure conditions are lower than temperature andpressure conditions used to fully infiltrate the at least partiallyleached PCD table 106.

The at least partially leached PCD table 106 described above in theembodiments shown in FIGS. 1A-1C and 2A-2B may be fabricated bysintering diamond particles in the presence of tungsten and/or tungstencarbide so that tungsten and/or tungsten carbide may be incorporatedinto the PCD table so-formed. FIGS. 3A-3D are cross-sectional viewsillustrating various stages in an embodiment of a method for fabricatinga PDC including a working region having tungsten and/or tungsten carbidetherein and the PDC so-formed. Referring to FIG. 3A, an assembly 300 maybe formed by positioning a metal-solvent catalyst layer 302 that issubstantially free of tungsten and/or tungsten carbide between a mass ofdiamond particles 304 and a cemented tungsten carbide substrate 306(e.g., a cobalt-cemented tungsten carbide substrate). The assembly 300may be subjected to HPHT conditions that are the same or similar to thatused on the assembly 100 shown in FIG. 1A.

Referring to FIG. 3B, during the HPHT process, metal-solvent catalystfrom the metal-solvent catalyst layer 302 may be liquefied and sweepsthrough the diamond particles 304 to sinter the diamond particles andform a PCD table 308 comprising bonded diamond grains (i.e.,diamond-to-diamond bonding) defining interstitial regions. Because thevolume of the metal-solvent catalyst layer 302 is selected so that it isnot sufficient to fill the volume of all of the interstices between thediamond particles 304, metal-solvent catalyst from the substrate 306also sweeps in carrying tungsten and/or tungsten carbide from thesubstrate 306. A PCD table 308 so-formed during HPHT process is bondedto the substrate 306. The PCD table 308 includes a first region 310adjacent to the substrate 306 that includes tungsten and/or tungstencarbide swept-in from the substrate 306 present in the interstitialregions thereof and a second region 312 remote from the substrate 306that is substantially free of tungsten and/or tungsten carbide. Thetungsten may be present in the first region 310 in a number of differentphases, such as one or more of the following phases: a metal-solventcatalyst alloy (e.g., a cobalt-tungsten alloy) including tungsten as analloying element and substantially pure tungsten. The volume of themetal-solvent catalyst layer 302 may be selected so that the secondregion 312 exhibits a thickness substantially greater than the firstregion 310. In this embodiment, the metal-solvent catalyst within theinterstitial regions between bonded diamond grains of the PCD table 308may be leached from the second region 312 relatively easier because itdoes not have tungsten and/or tungsten carbide therein.

Referring to FIG. 3C, the PCD table 308 may be separated from thesubstrate 306 by grinding material from the substrate 306 or anothersuitable material removal process. The separated PCD table 308′ may beleached to remove substantially all of the metal-solvent catalysttherefrom to form an at least partially leached PCD table 308″ shown inFIG. 3D. For example, the metal-solvent catalyst may be leached from thefirst region 310 using hydrofluoric acid and the metal-solvent catalystin the second region 312 may be leached using a less aggressive solutionof nitric acid, hydrochloric acid, or mixtures thereof.

Referring to FIG. 3E, the at least partially leached PCD table 308″ maybe employed to form a PDC, such as the PDC 112 shown in FIG. 1B, byorienting the second region 312 that is substantially free of tungstenand/or tungsten carbide positioned in proximity to the substrate 104 andadjacent to the silicon-cobalt containing layer 102. The first region310 of the at least partially leached PCD table 308″ that includestungsten and/or tungsten carbide therein is oriented remote from thesubstrate 104 so that a working region of a PDC ultimately formed whenthe assembly shown in FIG. 3E is subject to an HPHT process includestungsten and/or tungsten carbide to provide a wear resistant workingregion due to the presence of tungsten and/or tungsten carbide.

In another embodiment, a PCD table similar in construction to the PCDtable 308 may be fabricated by positioning the mass of diamond particles304 between the metal-solvent catalyst layer 302 and cemented tungstencarbide substrate 306 to form an assembly and subjecting the assembly toan HPHT process. The PCD table so-formed may be separated from thesubstrate 306, leached, and subsequently bonded to another substrate asdescribed above with respect to FIGS. 3C-3E.

FIGS. 4A-4C are cross-sectional views illustrating various stages in anembodiment of a method for fabricating a PDC in a single HPHT processand the PDC so-formed. Referring to FIG. 4A, an assembly 400 may beformed by positioning a mass of diamond particles 402 between a cementedtungsten carbide substrate 306 and a metal-solvent catalyst layer 404that is substantially free of tungsten and/or tungsten carbide. In oneembodiment, the metal-solvent catalyst layer 404 may comprise a thinfoil of cobalt, nickel, iron, or alloys thereof that is substantiallyfree of tungsten and/or tungsten carbide. In another embodiment, themetal-solvent catalyst layer 404 may comprise a green layer of particlesof cobalt, nickel, iron, alloys thereof, or combinations thereof thatare substantially free of tungsten and/or tungsten carbide. The assembly400 may be subjected to HPHT conditions similar to the HPHT conditionsused for HPHT processing the assembly 100 shown in FIG. 1A.

Referring to FIG. 4B, a PDC 406 is formed during the HPHT processincluding a PCD table 408 bonded to the substrate 306. During the HPHTprocess, the metal-solvent catalyst layer 404 is liquefied aninfiltrates into voids between diamond particles of the mass of diamondparticles 402 to effect intergrowth between the diamond particles tothereby form bonded diamond grains defining interstitial regions. Theinfiltrated metal-solvent catalyst from the metal-solvent catalyst layer404 occupies the interstitial regions between the bonded diamond grainswithin an upper region 410. The upper region 410 may exhibit a thicknessof about 150 μm to about 750 μm, such as about 250 μm to about 500 μm.The HPHT process may also liquefy a metal-solvent catalyst constituentof the substrate 306 that infiltrates into the mass of diamond particles402 to effect intergrowth between the diamond particles thereby formingbonded diamond grains (i.e., diamond-to-diamond bonding) defininginterstitial regions in a lower region 412 adjacent to the substrate306. The infiltrated metal-solvent catalyst constituent from thesubstrate 306 occupies the interstitial regions between the bondeddiamond grains within the lower region 412. The metal-solvent catalystconstituent that infiltrates from the substrate 306 may also carrytungsten and/or tungsten carbide. Accordingly, the metal-solventcatalyst constituent solidified within the interstitial regions of thelower region 412 includes tungsten and/or tungsten carbide.

Referring to FIG. 4C, the PCD table 408 may be subjected to a leachingprocess to remove metal-solvent catalyst from at least a portion of thePCD table 408. The metal-solvent catalyst infiltrated into the mass ofdiamond particles 402 from the metal-solvent catalyst layer 404 issubstantially free of tungsten and/or tungsten carbide, thereby enablingrelatively faster, deeper, and/or more effective leaching than themetal-solvent catalyst occupying the interstitial regions of the lowerregion 412. In one embodiment, substantially all of the metal-solventcatalyst of the upper region 410 may be selectively removed to a depth dmeasured from a working surface 414 of the PCD table 408. For example,one suitable leaching acid is a nitric acid solution. In one embodiment,the depth d may be about 150 μm to about 750 μm (e.g., about 250 μm toabout 500 μm) corresponding approximately to the thickness of the upperregion 410. By way of example, if the metal-solvent catalyst layer 404was omitted and metal-solvent catalyst from the substrate 306 sweptcompletely through the diamond particles 402 carrying tungsten and/ortungsten carbide, a PCD table so-formed may only be leached to a depthof about 200 μm even with leaching times in excess of 7 days. Thus,forming the upper region 410 to be substantially free of tungsten and/ortungsten carbide enables obtaining a leach depth d in the PCD table 408equal to or greater than a leach depth in a PCD table that has tungstenand/or tungsten carbide was distributed uniformly therethrough for agiven leaching time. If desired, in some embodiments, the metal-solventcatalyst present in the lower region 412 may also be depleted using amore aggressive acid, such as a hydrochloric acid.

The disclosed PDC embodiments may be used in a number of differentapplications including, but not limited to, use in a rotary drill bit(FIGS. 5A and 5B), a mining rotary drill bit (FIGS. 6A-6C), athrust-bearing apparatus (FIG. 7), a radial bearing apparatus (FIG. 8),a subterranean drilling system (FIG. 9), and a wire-drawing die (FIG.10). It should be emphasized that the various applications discussedabove are merely some examples of applications in which the PDCembodiments may be used. Other applications are contemplated, such asemploying the disclosed PDC embodiments in friction stir welding tools.

FIG. 5A is an isometric view and FIG. 5B is a top elevation view of anembodiment of a rotary drill bit 500. The rotary drill bit 500 includesat least one PDC configured according to any of the previously describedPDC embodiments. The rotary drill bit 500 comprises a bit body 502 thatincludes radially and longitudinally extending blades 504 with leadingfaces 506, and a threaded pin connection 508 for connecting the bit body502 to a drilling string. The bit body 502 defines a leading endstructure for drilling into a subterranean formation by rotation about alongitudinal axis 510 and application of weight-on-bit. At least one PDCcutting element, configured according to any of the previously describedPDC embodiments (e.g., the PDC 112 shown in FIG. 1C), may be affixed torotary drill bit 500. With reference to FIG. 5B, a plurality of PDCs 512are secured to the blades 504. For example, each PDC 512 may include aPCD table 514 bonded to a substrate 516. More generally, the PDCs 512may comprise any PDC disclosed herein, without limitation. In addition,if desired, in some embodiments, a number of the PDCs 512 may beconventional in construction. Also, circumferentially adjacent blades504 define so-called junk slots 518 therebetween, as known in the art.Additionally, the rotary drill bit 500 may include a plurality of nozzlecavities 520 for communicating drilling fluid from the interior of therotary drill bit 500 to the PDCs 512.

FIGS. 6A-6C are, respectively, a perspective view, a side elevationview, and a top elevation view of an embodiment of a mining rotary drillbit 600. The rotary drill bit 600 is suitably configured for drillingboreholes in a formation (i.e., configured as a roof drill bit), such asdrilling boreholes in an unsupported roof of a tunnel in, for example, acoal mine. The rotary drill bit 600 includes a bit body 602 that may beformed from a machinable steel, a hardfaced bit body, and aninfiltrated-carbide material (e.g., infiltrated tungsten carbide orso-called “matrix” material). The bit body 602 includes a head portion604 and a shaft portion 606 extending from the head portion 604. Theshaft portion 606 may include threads 608 or another suitable couplingportion configured for connecting the rotary drill bit 600 to a drillingmachine (not shown) operable to rotate the rotary drill bit 600 aboutthe rotation axis A and apply a thrust load along the rotation axis A todrill a borehole in a formation.

One or more PDCs 610 may be mounted to corresponding mounting portionsformed in the head portion 604 by, for example, brazing or press-fittingwithin a pocket or recess (not shown) formed in the bit body 602. EachPDC 610 may be configured according to any of the PDC embodimentsdisclosed herein, such as the PDC 112 shown in FIG. 1C. Each PDC 610includes a substrate 612 bonded to a PCD table 614. Each PCD table 614may each include a generally planar working surface 616 and a peripheralcutting edge 618. According to various embodiments, each peripheralcutting edge 618 may define an arc (e.g., an arcuate edge forming an arcof about 90° to about 190°), may define part of a perimeter of atriangle (e.g., substantially linear edges that intersect), may definepart of perimeter of a rectangle, may define part of a perimeter of anoval, or may define part of a perimeter of another selected shape. Eachcutting edge 618 may extend to a location at or proximate to therotation axis A or pass through the rotation axis A to eliminate anycoring effect during drilling of a formation.

The working surface 616 of each PDC 610 may be oriented in generallyopposite directions, and further oriented at a selected negative backrake angle, θ_(brk) and at a selected negative side rake angle, θ_(srk)to place the working surfaces 616 predominately in compression duringdrilling a formation. Referring to FIG. 6B, each working surface 616 maybe tilted about a reference axis by the negative back rake angle,θ_(brk), with the negative back rake angle, θ_(brk), being the anglebetween one of the working surfaces 616 and a reference plane x-x. Thereference axis is generally perpendicular to the rotation axis A andlies in the reference plane x-x with the rotation axis A. In oneembodiment, the negative back rake angle, θ_(brk), may be about 5degrees to about 35 degrees, and more particularly about 10 degrees toabout 25 degrees. Referring to FIG. 6C, each working surface 616 mayalso tilted about the rotation axis A by the negative side rake angle,θ_(srk), with the negative side rake angle, θ_(srk), being the anglebetween one of the working surfaces 616 and the reference plane x-x. Inone embodiment, the negative side rake angle, θ_(srk), may be about 2degrees to about 20 degrees, more particularly about 4 degrees to about10 degrees, and even more particularly about 4 degrees to about 9degrees.

FIGS. 5A-5B and 6A-6C are merely a few of many possible embodiments ofrotary drill bits that may employ at least one cutting elementfabricated and structured in accordance with the disclosed PDCembodiments, without limitation. Other earth-boring tools or drillingtools, including, for example, core bits, roller-cone bits, fixed-cutterbits, eccentric bits, bicenter bits, reamers, reamer wings, or any otherdownhole tool including PDCs, without limitation, may employ at leastone cutting element that comprises a PDC fabricated and structured inaccordance with the disclosed embodiments.

The PDC embodiments disclosed herein (e.g., the PDC 112 shown in FIG.1C) may also be utilized in applications other than rotary drill bits.For example, the disclosed PDC embodiments may be used in thrust-bearingassemblies, radial bearing assemblies, wire-drawing dies, artificialjoints, machining elements, and heat sinks.

FIG. 7 is an isometric cut-away view of an embodiment of athrust-bearing apparatus 700 that may utilize any of the disclosed PDCembodiments as bearing elements. The thrust-bearing apparatus 700includes respective thrust-bearing assemblies 702. Each thrust-bearingassembly 702 includes an annular support ring 704 that may be fabricatedfrom a material, such as carbon steel, stainless steel, or anothersuitable material. Each support ring 704 includes a plurality ofrecesses (not labeled) that receives a corresponding bearing element706. Each bearing element 706 may be mounted to a corresponding supportring 704 within a corresponding recess by brazing, press-fitting, usingfasteners, or another suitable mounting technique. One or more, or allof bearing elements 706 may be configured according to any of thedisclosed PDC embodiments. For example, each bearing element 706 mayinclude a substrate 708 and a PCD table 710, with the PCD table 710including a bearing surface 712.

In use, the bearing surfaces 712 of one of the thrust-bearing assemblies702 bears against the opposing bearing surfaces 712 of the other one ofthe bearing assemblies 702. For example, one of the thrust-bearingassemblies 702 may be operably coupled to a shaft to rotate therewithand may be termed a “rotor.” The other one of the thrust-bearingassemblies 702 may be held stationary and may be termed a “stator.”

FIG. 8 is an isometric cut-away view of an embodiment of a radialbearing apparatus 800 that may utilize any of the disclosed PDCembodiments as bearing elements. The radial bearing apparatus 800includes an inner race 802 positioned generally within an outer race804. The outer race 804 includes a plurality of bearing elements 806affixed thereto that have respective bearing surfaces 809. The innerrace 802 also includes a plurality of bearing elements 810 affixedthereto that have respective bearing surfaces 812. One or more, or allof the bearing elements 806 and 810 may be configured according to anyof the PDC embodiments disclosed herein. The inner race 802 ispositioned generally within the outer race 804 and, thus, the inner race802 and outer race 804 may be configured so that the bearing surfaces808 and 812 may at least partially contact one another and move relativeto each other as the inner race 802 and outer race 804 rotate relativeto each other during use.

The radial-bearing apparatus 800 may be employed in a variety ofmechanical applications. For example, so-called “roller cone” rotarydrill bits may benefit from a radial-bearing apparatus disclosed herein.More specifically, the inner race 802 may be mounted or affixed to aspindle of a roller cone and the outer race 804 may be affixed to aninner bore formed within a cone and that such an outer race 804 andinner race 802 may be assembled to form a radial-bearing apparatus.

Referring to FIG. 9, the thrust-bearing apparatus 700 and/or radialbearing apparatus 800 may be incorporated in a subterranean drillingsystem. FIG. 9 is a schematic isometric cut-away view of an embodimentof a subterranean drilling system 900 that includes at least one of thethrust-bearing apparatuses 600 shown in FIG. 7. The subterraneandrilling system 900 includes a housing 902 enclosing a downhole drillingmotor 904 (i.e., a motor, turbine, or any other device capable ofrotating an output shaft) that is operably connected to an output shaft906. A first thrust-bearing apparatus 600 ₁ (FIG. 7) is operably coupledto the downhole drilling motor 904. A second thrust-bearing apparatus600 ₂ (FIG. 7) is operably coupled to the output shaft 906. A rotarydrill bit 909 configured to engage a subterranean formation and drill aborehole is connected to the output shaft 906. The rotary drill bit 909is shown as a roller cone bit including a plurality of roller cones 910.However, other embodiments may utilize different types of rotary drillbits, such as a so-called “fixed cutter” drill bit shown in FIGS. 5A and5B. As the borehole is drilled, pipe sections may be connected to thesubterranean drilling system 900 to form a drill string capable ofprogressively drilling the borehole to a greater depth within the earth.

A first one of the thrust-bearing assemblies 602 of the thrust-bearingapparatus 600 ₁ is configured as a stator that does not rotate and asecond one of the thrust-bearing assemblies 602 of the thrust-bearingapparatus 600 ₁ is configured as a rotor that is attached to the outputshaft 906 and rotates with the output shaft 906. The on-bottom thrustgenerated when the drill bit 908 engages the bottom of the borehole maybe carried, at least in part, by the first thrust-bearing apparatus 700₁. A first one of the thrust-bearing assemblies 702 of thethrust-bearing apparatus 700 ₂ is configured as a stator that does notrotate and a second one of the thrust-bearing assemblies 702 of thethrust-bearing apparatus 700 ₂ is configured as a rotor that is attachedto the output shaft 906 and rotates with the output shaft 906. Fluidflow through the power section of the downhole drilling motor 904 maycause what is commonly referred to as “off-bottom thrust,” which may becarried, at least in part, by the second thrust-bearing apparatus 700 ₂.

In operation, drilling fluid may be circulated through the downholedrilling motor 904 to generate torque and effect rotation of the outputshaft 906 and the rotary drill bit 908 attached thereto so that aborehole may be drilled. A portion of the drilling fluid may also beused to lubricate opposing bearing surfaces of the bearing elements 706of the thrust-bearing assemblies 702.

FIG. 10 is a side cross-sectional view of an embodiment of awire-drawing die 1000 that employs a PDC 1002 fabricated in accordancewith the principles described herein. The PDC 1002 includes an inner,annular PCD region 1004 comprising any of the PCD tables describedherein that is bonded to an outer cylindrical substrate 906 that may bemade from the same materials as the substrate 104 shown in FIG. 1A. ThePCD region 1004 also includes a die cavity 908 formed therethroughconfigured for receiving and shaping a wire being drawn. Thewire-drawing die 1000 may be encased in a housing (e.g., a stainlesssteel housing), which is not shown, to allow for handling.

In use, a wire 1010 of a diameter d₁ is drawn through die cavity 1008along a wire drawing axis 1012 to reduce the diameter of the wire 1010to a reduced diameter d₂.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. Additionally, the words “including,”“having,” and variants thereof (e.g., “includes” and “has”) as usedherein, including the claims, shall have the same meaning as the word“comprising” and variants thereof (e.g., “comprise” and “comprises”) andmean “including, but not limited to.”

The invention claimed is:
 1. A polycrystalline diamond compact,comprising: a substrate; and a preformed polycrystalline diamond tableincluding an interfacial surface bonded to the substrate and an opposingworking surface, the preformed polycrystalline diamond table including:a proximal region directly bonded to the substrate, the proximal regionextending from the interfacial surface to an intermediate locationwithin the preformed polycrystalline diamond table that consistsessentially of diamond grains having diamond-to-diamond bondingtherebetween and a metallic infiltrant infiltrated into interstitialregions between the diamond grains; and a distal region extending fromthe working surface to the intermediate location that is substantiallyfree of the metallic infiltrant, portions of the metallic infiltrantexposed through at least partially empty interstitial regions of thedistal region having a surface structure characteristic of not beingchemically etched, the distal region having a residual amount ofmetal-solvent catalyst therein.
 2. The polycrystalline diamond compactof claim 1 wherein the metallic infiltrant comprises iron, nickel,cobalt, or alloys thereof.
 3. The polycrystalline diamond compact ofclaim 1 wherein the metallic infiltrant comprises tungsten, tungstencarbide, or combinations thereof.
 4. The polycrystalline diamond compactof claim 1 wherein the intermediate location is at a depth, from theworking surface of the preformed polycrystalline diamond table, of atleast about 50 μm.
 5. The polycrystalline diamond compact of claim 1wherein the intermediate location is at a depth, from the workingsurface of the preformed polycrystalline diamond table, of about 50 μmto about 2000 μm.
 6. The polycrystalline diamond compact of claim 1wherein the substrate comprises a cemented carbide substrate includingthe metallic infiltrant therein.
 7. The polycrystalline diamond compactof claim 1 wherein the preformed polycrystalline diamond table comprisesa boundary between the proximal region and the distal region exhibitinga nonplanar irregular profile characteristic of the metallic infiltranthaving been infiltrated into the preformed polycrystalline diamondtable.
 8. A polycrystalline diamond compact, comprising: a substrate;and a preformed polycrystalline diamond table including an interfacialsurface bonded to the substrate and an opposing working surface, thepreformed polycrystalline diamond table including: a proximal regiondirectly bonded to the substrate, the proximal region extending from theinterfacial surface to an intermediate location within the preformedpolycrystalline diamond table that consists essentially of diamondgrains having diamond-to-diamond bonding therebetween and a metallicinfiltrant in interstitial regions between the diamond grains; a distalregion extending from the working surface to the intermediate locationthat is substantially free of the metallic infiltrant, portions of themetallic infiltrant exposed through at least partially emptyinterstitial regions of the distal region having a surface structurecharacteristic of not being chemically etched, the distal region havinga residual amount of metal-solvent catalyst therein; and a boundarybetween the proximal region and the distal region exhibiting a nonplanarirregular profile characteristic of the metallic infiltrant having beeninfiltrated into the preformed polycrystalline diamond table.
 9. Thepolycrystalline diamond compact of claim 8 wherein the metallicinfiltrant comprises iron, nickel, cobalt, or alloys thereof.
 10. Thepolycrystalline diamond compact of claim 8 wherein the metallicinfiltrant comprises tungsten, tungsten carbide, or combinationsthereof.
 11. The polycrystalline diamond compact of claim 8 wherein theintermediate location is at a depth, from the working surface of thepreformed polycrystalline diamond table, of at least about 50 μm. 12.The polycrystalline diamond compact of claim 8 wherein the intermediatelocation is at a depth, from the working surface of the preformedpolycrystalline diamond table, of about 50 μm to about 2000 μm.
 13. Thepolycrystalline diamond compact of claim 8 wherein the substratecomprises a cemented carbide substrate including the metallic infiltranttherein.